Set state list of data type has multiple attributes

I am working on a marketplace, the merchant can add products.
each product has basic details all saved in one database table: “products”.
example: product name, in stock?, reference …etc.

for each product has unique attributes saved in a different table (table: product Specs) fields:
Product → type: product
spec name → type: text
value → type: text
unit of measure → text

on the page, I created a custom state list (type: product specs) to add the product specs in it before saving them to the database.
Spec Form:
input: spec name
input spec value
input unit of measure

Spec name: Age
spec value: 10
unite of measure: years

Spec name: speed
spec value: 400
unite of measure: hp

my question how can I access the items in the custom state of type “product specs”? and save the values one by one from the input fields? this is driving me crazy because I couldn’t find any video talking about it.

I hope I explained the situation clearly.

What would be the alternative, to save a record of multiple attributes in a custom state list, and once everything is confirmed save it to the database. I managed to work with lists has single attribute, not multiple attributes.